The present invention relates to a system for the detection of newton ring mura.
Flat panel displays, such as for example, a liquid crystal display, a plasma display, and an organic electroluminescent display, preferably display a uniform image on the display when provided a uniform grey level input. In the case of liquid crystal displays, mura type defects are generally caused by process flaws related to cell assembly, which affect the transmission of light through the display and are generally objectionable to viewers. The cyclical nature, randomness, and low contrast of such mura type defects makes accurate detection and classification difficult, especially for liquid crystal displays. With manufacturing variations in various components of a display, not all devices are capable of providing uniform display properties for the entire display area. Due to such irregularities, the display devices are visually inspected to determine whether or not they display a sufficiently uniform image.
As a general matter, one particular class of irregularity may be referred to as a newton ring mura which are generally a relatively small circular shaped non-uniformity. In general, the newton ring mura is a color based non-uniformity that appears as a ring.
One technique to detect such newton ring mura defects in a display is by manual visual inspection. An inspector looks at each display when presenting a uniform grey scale, and manually identifies and labels identified newton ring muras. This process of manual visual identification tends to be inconsistent and the identification heavily dependent on the skills and expertise of the inspectors. Also different inspectors take a different amount of time to inspect a display, together with a limited number of skilled inspectors, which limits the inspection of mass produced displays. In addition, inspectors tend to have variable performance over time due to fatigue.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.